Color filter and manufacturing method therefor

ABSTRACT

The color filter of the present invention comprises ink films colored by ink drops  140  inside openings  111  enclosed by banks  112  demarcated and formed on a substrate  110.  The banks  112  have a laminar structure comprising a metal film  120  and a photosensitive organic thin film  130  from the substrate  110  side. The inks should contain a solvent having a high boiling point. The bank layer may also be configured so that the peripheral edges of the bottom surface thereof are positioned inside from the peripheral edges of the light blocking layers, so that the light blocking layers have exposed surfaces on the upper surface thereof where the bank layer is not superimposed. Thus color filters can be provided which exhibit outstanding contrast without coloring irregularities.

This is a Division of application Ser. No. 09/622,368 filed Aug. 16,2000, now U.S. Pat. No. 6,630,274, which in turn is a U.S. NationalStage Application, which claims the benefit of International ApplicationNo. PCT/JP99/07081 filed Dec. 16, 1999. The entire disclosure of theprior applications is hereby incorporated by reference herein in itsentirety.

TECHNICAL FIELD

This invention relates to color filters used in liquid crystal displayelements and the like, and more particularly to color filters, and to amanufacturing method therefor, that have a structure well suited tocolor filters wherein a minute droplet discharge method is applied whichis based on an ink jet method. The present invention also relates toliquid crystal display devices, electro-optical devices, and electronicequipment comprising such color filters, and to manufacturing methodstherefor.

BACKGROUND ART

The demand for liquid crystal color displays has been increasing rapidlyin recent years in conjunction with the advances being made in personalcomputers in general and portable personal computers in particular. Inresponding to this demand, high priority is now being given toestablishing means for supplying beautiful displays at reasonable cost.At the same time, in recent years, protecting the environment has becomea big issue, and high priority is being given to making improvements inor converting to processes that will reduce the impact on theenvironment.

A number or methods are known conventionally for manufacturing colorfilters. One example is to pattern a light blocking material that is athin film of chromium by photolithography and etching to form a blackmatrix. Then red, green, and blue photosensitive resins are applied tothe gaps in that black matrix, one color at a time, by a spin coatingmethod or the like, after which patterning is done by photolithography.In that way a color matrix can be configured wherein red, green, andblue coloring layers are deployed adjacent to each other. With thismanufacturing method, however, the photolithographic process must berepeated for each of the red, green, and blue colors. Not only so, butthe elimination of unneeded portions when patterning each color resultsin losses of photosensitive resist material. Thus this method tends tohave a high impact on the environment and produce high-cost colorfilters.

In Japanese Patent Laid-Open Publication No. S59-75205, a method isproposed wherein an ink jet method is employed. In this method, inkcoating gap partitions are formed in a matrix pattern on a transparentsubstrate, using a material that exhibits low ink wettability, afterwhich a coloring layer is formed by applying non-photosensitive coloringmaterials inside the partitions using an ink jet method. By using thismanufacturing method, the tediousness of the photolithographic processescan be alleviated, and it has become possible to reduce color materiallosses. Subsequently, many color filter manufacturing methods have beenproposed which employ non-photosensitive coloring material applicationprocesses based on an ink jet method.

In one example, a chromium film is formed on a glass substrate using asputtering film-forming method, this is etched in a prescribed patternto form openings (pixels or light-transmitting areas), and thoseopenings are filled with ink drops, thus manufacturing a color filter.

In many methods, a black photosensitive resin composition is used as thelight blocking material, and, thereby, a bank layer is formed topartition the areas that are to be coated with coloring materials in amatrix pattern. In these methods, the surface of the bank layer thatfunctions as a black matrix is imparted with an ink repelling quality,and color mixing caused by bank layer overflows in the color materialapplication process is prevented.

In the art disclosed in Japanese Patent Laid-Open Publication No.H4-195102, Japanese Patent Laid-Open Publication No. H7-35915, JapanesePatent Laid-Open Publication No. H7-35917, and Japanese Patent Laid-OpenPublication No. H10-142418, for example, in every case, a difference inink wettability is elicited between the bank layer and the transparentsubstrate by the selection of the resin materials configuring the blackmatrix and by surface processing done on the surface of the transparentsubstrate in areas where coloring materials are applied.

When a chromium film is formed by a sputtering film forming method toform the banks, however, the limitation on the film thickness is about0.2μ, and banks having sufficient height (0.5μ to 10μ) for ink fillingcannot be formed. Also, when the interiors of openings enclosed by banksare filled with ink drops by the ink jet method, it is necessary toprevent the ink drops from crossing over the banks so that they overflowinto neighboring pixels, making it necessary to impart ink affinity tothe substrate and ink repellency to the banks. Hence it is preferablethat the upper parts of the banks be configured by materials such asorganic materials that may be readily subjected to ink repellencytreatment.

Thereupon, in view of the problems noted in the foregoing, an object ofthe present invention is to provide color filters and liquid crystalelements comprising banks that are ideal for methods of manufacturingcolor filters by filling banks with ink by the ink jet method. Anotherobject thereof is to provide a color filter manufacturing method wellsuited to the ink jet method.

When, on the other hand, a photosensitive black resin composition isused for the light blocking material in forming the black matrix, it isvery difficult to obtain the right balance between light transmissivityand resin hardness. In actual practice, film thickness variation in theblack matrix layer, which functions as the bank layer, is unavoidablebecause the film thickness is large. When a negative resist is used, forexample, where the film thickness is thick, portions develop in thelithographic process that do not adequately transmit light, whereuponunhardened portions remain. When such unhardened portions as these arepresent, it is sometimes not possible to obtain sufficient film strengthin the black matrix layer. Places where the film thickness is thin inthe black matrix layer, on the other hand, become semi-transparent sothat adequate light blocking properties are not obtained, sometimesleading to the occurrence of light leakage.

In recent years, color filters have become increasingly more highprecision, making it necessary to form very fine red, green, and bluepixels that are a few tens of μ square, with good coloring materialbonding, while minimizing color tone variation. With the conventionalart however, making the contact angles of the resin banks that demarcateand partition the pixels on the large size becomes a cause of pixelbonding flaws due to resin components spattering about the periphery. Inmethods which combine such dry etching processes as UV irradiation,plasma etching, and laser ablation for the purpose of preventing suchbonding flaws, selectively processing only the gap portions where theink is to be deployed becomes increasingly difficult the finer thepatterns become. For this reason, the bank portions also end up gettingprocessed at the same time, which only causes the contact angle todecline significantly. That is, attempts to make the difference incontact angle between the transparent substrate surface portion wherethe coloring material of the increasingly minute pixels adheres and theblack resin banks that demarcate those portions particularly large arenot very effective, especially in view of the high degree of technicaldifficulty involved.

Forming the thicknesses wherewith coloring materials adhere evenly inorder to minimize variation in color tone in even more minute pixels isa very important process in determining color filter quality, but suchprocesses are not elucidated in the prior art.

There is also nothing elucidated in the prior art about techniques forforming adjacent red, green, and blue deployments in such minute pixels,simultaneously, and without ink color mixing.

The present invention, devised for the purpose of radically resolvingsuch technical difficulties inherent in the prior art, provides a methodwherewith inks, as the coloring material, can be efficiently deployed inlight blocking material matrix gaps by the ink jet method. Not only so,but a method is provided wherewith, because the ink film thickness ismade uniform and given high bonding properties, high-contrast colorfilters are manufactured without pixel flaws or color toneirregularities. Another object is to provide a manufacturing method forliquid crystal display devices wherein such color filters areincorporated.

Another object is to provide color filters that comprise both lightblocking regions having adequate light blocking properties andtransparent regions wherein there is no color mixing, together with amanufacturing method therefor.

Yet another object of the present invention is to provideelectro-optical devices and electronic equipment having such colorfilters as those described in the foregoing.

DISCLOSURE OF THE INVENTION

The color filter of the present invention is a color filter that, insidethe openings enclosed by the banks formed for demarcation on thesubstrate, comprises ink films (coloring layers) colored by inks. Thebanks have a structure wherein, from the substrate side, a metal filmand a photosensitive organic thin film are laminated. Because of thislaminar structure, not only can banks of sufficient height be formed,but treating the substrate surface for the inks (i.e. treating to givethe banks ink repellency and give the substrate ink affinity) becomeseasy.

The resist used for etching the metal film can be used as thephotosensitive organic thin film. When that is done, the process ofremoving unneeded resist after etching the metal layer can be omitted,so that the color filter manufacturing process can be simplified.

The photosensitive organic thin film can be selected from amongpolyimide films, acrylic resin films, polyhydroxy styrene films, novolacresin films, polyvinyl alcohol films, and cald resin films. Thisphotosensitive organic thin film can be given ink repellency by adding afluorine-based surfactant thereto. The fluorine-based surfactant used isa structure having perfluoroalkyl or derivative thereof, fluorobenzene,difluorobenzene, trifluorobenzene, perfluorobenzene, or fluorophenol orderivative thereof as the fluorine-containing group. Ink repellency canalso be imparted to the photosensitive organic thin film by mixing afluorine-based polymer therein. This fluorine-based polymer can beselected from among silicone rubber, vinylidene polyfluorides,fluoroolefins, vinyl ether-based copolymers, ethylene trifluoride,vinylidene fluoride copolymers, polytetrafluoroethylenes,perfluoroethylene propyline resins, and perfluoroalcoxy resins. Byadjusting the amount of such fluorine-based surfactant added or thefluorine-based polymer mixture ratio, the contact angle between thebanks and the ink—that is, the ink repellency of the banks—can beadjusted according to necessity.

The photosensitive organic thin film can be configured by laminating aplurality of photosensitive organic thin films. The metal film can alsobe made to function as a black matrix. In that case, it is preferablethat the composition of the metal film contain either chromium, nickel,tungsten, tantalum, copper, or aluminum.

In a color filter comprising a protective film that covers the banks andthe ink films, furthermore, it is preferable that the composition of theprotective film have bisphenol A or bisphenol fluorolene or the like inorder to satisfy the demands for heat resistance, transparency, andleveling properties. What is even more preferable is to make thecomposition of the protective layer the same as the composition of theorganic thin film, thus making it possible to prevent crawling orunevenness in the protective film formed on the banks, whereupon colorfilters for liquid crystal display elements can be provided whichexhibit outstanding contrast.

In the substrate surface treatment, the combination of the banks and theink should be set so that the contact angle between the banks and theink is 30 degrees or more but 60 degrees or less. If this contact angleis less than 30 degrees, the affinity between the banks and the inkrises, the quantity of ink adhering to the banks becomes large, and itwill become easy for coloring flaws to occur on the substrate. If thecontact angle exceeds 60 degrees, on the other hand, the ink repellencyof the bank relative to the ink becomes large, and it will become easyfor coloring flaws to develop on the substrate near the banks. Thecontact angle between the substrate and the ink, meanwhile, should be 30degrees or less. When consideration is given to the fact that inkaffinity is desired in the substrate, and to the pixel pitch in thecolor filter, this is seen to be a suitable range.

The liquid crystal display element of the present invention comprisesthe color filter described in the foregoing. By comprising that colorfilter, very minute liquid crystal display elements can be providedwhich exhibit no display unevenness or coloring unevenness.

The color filter manufacturing method of the present invention is amethod of manufacturing a color filter comprising ink films in theopenings enclosed by banks formed for demarcation on the substrate,comprising a first step for demarcating and forming a metal film on thesubstrate, a second step for forming the banks by forming aphotosensitive organic thin film on the metal film, and a third step forfiling the interiors of the openings with ink to form ink films. Bymaking the photosensitive organic thin film the resist for etching themetal film, the resist removal step can be omitted and the color filtermanufacturing process simplified. The second step may form the banks bylaminating a plurality of photosensitive organic thin films on the metalfilm. It is also permissible to provide, between the second and thirdsteps, a step for imparting ink affinity to the substrate surface byimplementing a plasma treatment using oxygen gas as the induction gas,and a step for imparting ink repellency to the banks by implementing aplasma treatment using a fluoride compound as the induction gas. Bythese plasma treatment steps, the banks can be made to exhibit inkrepellency and the substrate to exhibit ink affinity. The fluoridecompound used as the induction gas should be either carbon tetrafluoridegas, nitrogen trifluoride gas, or sulfur hexafluoride gas. The bank canalso be made ink-repellent by heating the substrate instead ofperforming the plasma treatment using the fluoride compound as theinduction gas.

The color filter manufacturing method of the present invention is alsocharacterized in that it has a step for forming a metal thin film matrixpattern that is a light blocking layer on the transparent substrate, astep for forming matrix banks with resin on the metal thin film lightblocking layer, and a step for directly applying ink in the gaps in thatmatrix pattern.

The liquid crystal display device manufacturing method of the presentinvention is characterized in that it has a step for forming a metalthin film matrix pattern that is a light blocking layer on thetransparent substrate, a step for forming matrix banks with resin onthat metal thin film light blocking layer so that they are roughlysuperimposed on the metal thin film matrix pattern, a step forsubjecting the entire surface patterned as described above to a dryetching process, a step for providing ink in the gaps of that matrix,and an overcoat application step for smoothing the upper surface, andalso a step for forming a color filter substrate that includes a stepfor forming thin film electrodes, a step for deploying an opposingsubstrate having pixel electrodes in opposition to the color filtersubstrate, and a step for filling the gap between the color filtersubstrate and the opposing substrate with a liquid crystal composition.

In the manufacturing method described in the foregoing, the step forforming the metal thin film light blocking layer matrix pattern on thetransparent substrate comprises a step for patterning the metal thinfilm layer by a photoresist etching method.

Included in the manufacturing method described in the foregoing is thefact of being a process for patterning the photosensitive resincomposition by a photoresist method with the banks that partition thegaps to which the inks are deployed superimposed on the metal thin filmmatrix pattern on the transparent substrate.

In the manufacturing method described in the foregoing, the step forobtaining a contact angle difference of 15° or more between the surfaceof the resin banks described above and water on the surface in the gapsin the transparent substrate partitioned by those banks comprises a stepfor performing simultaneous entire-surface dry etching on the resinsurface and substrate gap.

In the manufacturing method described in the foregoing, the step forproviding ink in the resin matrix pattern gaps comprises a step foreffecting the controlled provision of minute ink drops, from 6picoliters to 30 picoliters each, by an ink jet printing head.

The manufacturing method described in the foregoing includes the factthat the inks include a solvent having a high boiling point of from 150to 300° C., and are thermally hardened inks the compositions whereof areadjusted, by suitably establishing the drying conditions to settings ina natural atmosphere, 40 to 100° C. prebaking, and 160 to 240° C. finalbaking, so that the ink layer films on the surfaces in the substrategaps after application and drying are leveled and the film thickness ismade uniform.

In manufacturing color filters, by forming a light blocking layer matrixpattern on a transparent substrate, and providing red, green, and bluecoloring materials or inks of the necessary color tones in the gaps inthat matrix pattern so that there is no intermingling of colors, colorfilters of outstandingly high contrast can be obtained. When this isbeing done, a resin matrix pattern for demarcating the gaps in thematrix pattern noted above is formed so that it is superimposed on thelight blocking layer matrix pattern in order to prevent ink colormixing. Forming this matrix pattern made up of two layers and activatingthe surface to adjust the ink adhesion conditions prior to deploying theinks constitute one fundamental technology for manufacturing colorfilters.

In the present invention, a metal thin film is employed as the firstlayer light blocking layer in the matrix pattern made up of two layersas described above, and a matrix pattern is obtained by forming thatfilm to a thickness of 0.1 to 0.5μ and employing a photoresist etchingmethod. This thin film metal can be obtained using a technique such asvapor deposition, sputtering, or chemical vapor deposition. Aphotosensitive composition is employed for the second layer, a patternwhich is superimposed on the first layer is formed to a layer thicknessof 1.5 to 5μ, and patterning is done, again employing a photoresistmethod. The photosensitive composition employed in the second layer neednot be black in color, and liberal use can be made of the generallyavailable photosensitive compositions. The substrate gap surfaceswherein the second layer is patterned is exposed to all kinds ofcontaminating factors during the patterning process, whereupon thecontact angle with water rises, constituting an impairment later whendeploying the inks and forming uniform films. For that reason, afterpatterning, as a step preparatory to deploying the inks, the entiresurface is subjected to a dry etching operation. At that time, it isonly necessary to realize conditions such that the contact angle of thepattern gaps with water is restored to the initial transparent substratevalue, and there is no need whatever to selectively etch only the gaps.According to what has been learned, a difference of 15° or more in thecontact angle for water between the gap surfaces and the second layermaterial resin surface can be obtained by a dry etching method such asUV irradiation, plasma irradiation, or laser irradiation.

In the present invention, furthermore, focusing attention on the stepfor deploying inks to the matrix pattern gap surfaces, technology isperfected for accurately providing small ink drops of 6 to 30 picoliterseach, while controlling the number of drops, in minute pixeldemarcations that are 50μ square. In order to secure film thicknessuniformity in the ink coating films provided in the gap demarcations inthe matrix pattern, a solvent having a high boiling point is added tothe ink composition, thereby making it possible to improve ink levelingproperties, with significant effectiveness realized with a solventhaving a boiling point of 150 to 300° C. The means used together withthe addition of the high-boiling-point solvent for securing filmthickness uniformity in the ink coating films are controlling the dryingconditions after providing the ink, with it being appropriate to causedrying and hardening in the three steps of setting in a naturalatmosphere, prebaking in a middle temperature range at 40 to 100° C.,and final baking at 160 to 240° C.

The present invention also comprises the suppression of variation in thecolor tones of the thermally hardened ink coating films provided in thegaps of the matrix pattern, limiting that variation to a certain range.The regions where color tone variation must be considered are regionswithin the same pixel, within the same chip, and within the samesubstrate. In every one of these regions the color difference that isthe variation index can be held down to 3 or below.

In the color filters of the present invention, furthermore, lightblocking regions and light transmitting regions are deployed in aprescribed matrix pattern on a transparent substrate, with the lightblocking regions comprising a light blocking layer and a bank layerprovided on that light blocking layer, and the light transmittingregions configured by a coloring layers demarcated by the light blockingregions. In the bank layer, the peripheral edges of the bottom surfacethereof are positioned inside the peripheral edges of the light blockinglayer. The light blocking layer has an exposed surface on the uppersurface thereof whereon the bank layer is not superimposed. The coloringlayer is formed so that the peripheral edges thereof are notsuperimposed on the exposed surface of the light blocking layer.

In this color filter, the bank layer has the peripheral edges of thebottom surface thereof positioned inside the peripheral edges of thelight blocking layer. That is, in the plan-view pattern, part of thelight blocking layer is exposed, formed so that the width thereof issmaller than the light blocking layer. By having this exposed surface,non-transmitting portions are formed at the peripheral edges of thecoloring layer where it is difficult to obtain uniform film thickness,which non-transmitting portions function as light transmitting regions.As a result, in the color filters of the present invention, the filmthickness of the light transmitting portions of the coloring layer thatfunction as light transmitting regions can be made uniform, so that suchflaws as color tone irregularities do not tend to occur, and highcontrast is effected.

Furthermore, by providing the light blocking layer and the bank layer,the light blocking function and the demarcation function of the coloringlayer can each be provided independently, so that both functions can bemanifested without fail. As a result, in the color filters of thepresent invention, pixel flaws caused by inadequate light blocking orcolor mixing of the color materials configuring the coloring layer donot tend to arise. Furthermore, by dividing the functions in thismanner, ideal materials for configuring the light blocking layer and thebank layer can be selected from a wide range, and this is a benefit alsoin terms of production costs.

With the color filters of the present invention, moreover, in the banklayer, the peripheral edges of the bottom surface thereof are positionedinside the peripheral edges of the light blocking layer. In other words,the side surfaces of the bank layer are drawn back farther than the sidesurfaces of the light blocking layer, wherefore a step is formed on thelight blocking layer. The inks that constitute the color materials canbe held by this step, wherefore, even if some of the ink layers overflowthe bank layer while forming the coloring layer, that ink is preventedfrom flowing onto the exposed surface of the substrate in adjacentcoloring layer formation regions. For that reason, color mixing in thecoloring layer caused by ink mixing can be prevented from occurring. Asa result, flaws such as color tone irregularities do not tend to developin the color filters of the present invention, and high contrast iseffected.

It is preferable that the color filters of the present invention takethe following modes.

It is preferable that the exposed surface of the light blocking layerdescribed earlier be continuous around the periphery of the lighttransmitting region. By this exposed surface being continuous, theoperating effects of the color filters described earlier can be elicitedmore definitely. The width of that exposed surface of the light blockinglayer should be from 3 to 10μ in view of the non-uniformity of the filmthickness of the coloring layer about the peripheral edges thereof.

It is preferable that the light blocking layer be configured of a metallayer. When the light blocking layer is configured of a metal layer,light blocking performance that is both even and adequate can beobtained with small film thickness. In the interest of light blockingperformance and film formation performance, the thickness of the metallayer configuring the light blocking layer should be from 0.1 to 0.5μ.

The film thickness of the bank layer should be from 1 to 5μ in view ofthe fact that the ink layers are held so that the ink deployed in thecoloring layer formation regions does not overflow when forming thecoloring layer.

The cross-sectional shape of the bank layer in the width dimension maybe roughly trapezoidal with the width wider on the substrate side. Withthe bank layer having such a structure as this, the uniformity of thecoloring layer can be enhanced even further without sacrificing theeffective surface area of the coloring layer.

Based on the color filters of the present invention, colored lighttransmitting regions of even film thickness can be obtained, and thoselight transmitting regions can manifest good optical characteristics,with the variation in color tone in the same pixel, in the same chip,and in the same substrate held down preferably to a color difference of3 or less, and even more preferably to a color difference of 2 or less.

The color filter manufacturing method of the present invention comprisesthe following steps (a) to (c):

(a) a step for forming a light blocking layer having a prescribed matrixpattern on a transparent substrate;

(b) a step for forming a bank layer having a prescribed matrix patternon the light blocking layer, wherewith the peripheral edges of thebottom surface of the bank layer are positioned inside the outer edgesof the light blocking layer, and some of the upper surface of that lightblocking layer is formed in an exposed condition; and

(c) a step for forming coloring layers in coloring region formationregions demarcated by the light blocking layer and the bank layer,wherewith the coloring layers are formed on the substrate, and theperipheral edges thereof are formed in a condition wherein they aresuperimposed on the exposed surface on the upper surface of the lightblocking layer.

Based on this color filter manufacturing method, the color filters ofthe present invention described earlier can be obtained by simple steps.Also, the red, green, and blue colored color materials (inks) can bedeployed in the coloring layer formation regions by the bank layer in acondition wherein there is no color mixing, whereupon it is possible toobtain high-contrast color filters exhibiting no flaws such as colortone irregularities.

In addition, the peripheral edges of the bottom surface of the banklayer are positioned inside from the peripheral edges of the lightblocking layer. That is, the side surfaces of the bank layer are fartherwithdrawn than the side surfaces of the light blocking layer, whereforea step is formed on the light blocking layer. As described already, theoccurrence of color mixing in the coloring layer due to ink mixing canbe prevented by that step. As a consequence, based on the color filtermanufacturing method of the present invention, high-contrast colorfilters can be obtained wherein flaws such as color tone irregularitiesdo not tend to occur.

In step (a) above, the light blocking layer should be formed by firstforming the metal layer on the substrate, and then patterning that metallayer by photolithography and etching. The advantages of using a metallayer for the light blocking layer were noted earlier and so are notfurther described here. This metal layer can be formed by a method suchas vapor deposition, sputtering, or chemical vapor deposition.

In step (b) above, the bank layer should be formed by first forming aphotosensitive resin layer on the substrate whereon the light blockinglayer has been formed, and then patterning by photolithography. Thisbank layer need not be light blocking, and so need not be black, so thatit is possible to select broadly from among the commonly availablephotosensitive resin compositions.

It is preferable that the entire surface of the substrate whereon lightblocking regions have been formed be subjected to a surface treatmentprior to the process of forming the coloring layer in step (c) above. Bythis surface treatment, the difference in the contact angle for waterbetween the bank layer surface and the substrate surface should be made15° or greater. Thus, by subjecting the substrate surface to a surfacetreatment prior to forming the coloring layer, contaminating substancesadhering to the exposed surface in the coloring layer formation regionson the substrate are removed, whereupon it is possible to make thecontact angle of that exposed surface with water small and to enhanceink wettability.

In other words, by controlling the contact angle with water of theexposed surface of the substrate and the bank layer, ink can be deployedin a condition wherein it adheres well to the exposed surface in thecoloring layer formation region, and the ink is prevented from crossingover the bank layer and overflowing by the ink repelling property of thebank layer. The method used for this surface treatment can beultraviolet irradiation, plasma irradiation, laser irradiation, or dryetching involving an etching gas.

In step (c) above, for the coloring layer, it is preferable that thecoloring layer formation regions be provided with inks using an ink jetprinting head. By using that method, the color filters of the presentinvention can be formed simply and with few steps. That is, by formingthe coloring layers with the ink jet method, the step of usingphotolithography to perform patterning can be eliminated, so the stepscan be simplified. Also, because inks are deployed in the coloring layerformation regions by the ink jet method, inks can be deployed only inthe regions where they are needed. For that reason, there is no loss ofcolor materials as occurs when unneeded portions are removed inpatterning by photolithography, so the color filter manufacturing costscan be reduced.

With the ink jet method, the ink should be delivered in minute ink dropsof from 6 to 30 picoliters each. By controlling the number of theseminute ink drops, inks can be exactingly deployed in minute regions offrom 40 to 100μ square, for example.

In step (c) above, it is preferable that the ink forming the coloringlayer contain a solvent having a boiling point of from 150 to 300° C. Byadding a solvent with a high boiling point to the ink, the ink dryingspeed can be decelerated. As a result, the ink leveling properties canbe improved and the film thickness of the coloring layer made moreuniform. For this solvent of high boiling point, at least one type ofsolvent can be used that is selected from among butylbarbitol acetate,methoxybutyl acetate, ethoxyethyl propionate, and methoxy-2-propylacetate. But this poses no limitation, and the solvent can be selectedfrom a wide range of solvents having a boiling point of from 150 to 300°C., taking pigment diffusability or dye solubility into consideration.

In step (c) above, it is preferable that the inks used for forming thecoloring layers, after being deployed in the coloring layer formingregions, be subjected to a combination, depending on the ink properties,of at least either setting in a natural atmosphere or prebaking at 40 to100° C., and final baking at 160 to 300° C. By selecting thatcombination and the ink drying conditions while taking the control ofthe ink drying speed discussed earlier into consideration, even greaterfilm thickness uniformity can be definitely realized in the coloringlayers.

The electro-optical device relating to the present invention comprisesone of the color filters described in the foregoing, an opposingsubstrate deployed at a prescribed interval with that color filter, andan electro-optical material layer deployed between that color filter andthat opposing plate.

The electronic equipment relating to the present invention comprises theelectro-optical device of the present invention.

Based on the electro-optical device and electronic equipment relating tothe present invention, costs can be reduced, as with the operatingeffects of the color filters of the present invention described earlier,and high-contrast displays can be effected with no pixel flaws such ascolor tone irregularities. If a liquid crystal material layer is usedfor the electro-optical material layer noted earlier, moreover, liquidcrystal display devices can be configured that can produce high-contrastdisplays with no pixel flaws such as color tone irregularities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional manufacturing process diagram for a colorfilter according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional manufacturing process diagram for a colorfilter according to a modification of the first embodiment;

FIG. 3 is a diagram representing ink film coloring conditions;

FIG. 4 is a diagram of the relationship between surface area and theangle wherewith ink drops discharged on a substrate contact a glasssubstrate;

FIG. 5 is a diagram representing the relationship between surface areaand the ink contact angle with a substrate when the contact widthrelative to the substrate is held constant;

FIG. 6 is a cross-sectional manufacturing process diagram for a colorfilter according to a second embodiment of the present invention;

FIG. 7 is a cross-sectional diagram representing the configuration of aliquid crystal display device of the present invention;

FIG. 8 is a diagram representing ink cross-sectional shapes when dryingafter ink deployment;

FIG. 9 is a partial cross-section that represents, in model form, acolor filter relating to a third embodiment of the present invention;

FIG. 10 is a cross-sectional diagram representing in model form aportion along the A—A line in FIG. 9;

FIG. 11 is a set of partial cross-sections that represent, in modelform, manufacturing processes for the color filter diagrammed in FIGS. 9and 10;

FIG. 12 is a set of partial cross-sections that represent, in modelform, manufacturing processes for the color filter diagrammed in FIGS. 9and 10;

FIG. 13 is a partial cross-section representing a modification of thecolor filter relating to the third embodiment;

FIG. 14 is a partial cross-section of a liquid crystal display devicewherein is employed an electro-optical device that comprises a colorfilter relating to the present invention;

FIG. 15 is a diagonal diagram that represents, in model form, a digitalstill camera that uses a color filter relating to the present invention;and

FIG. 16 is a diagonal diagram that represents, in model form, a personalcomputer that uses a color filter relating to the present invention.

In the drawings, item 110 is a substrate, 120 is a chromium film, 130 isa resist, 140 is ink, 150 is a protective film, 160 is a transparentelectrode, 101 is an electrode, 102 is an electrode, 103 is a powersupply, and 104 is an ink jet type recording head.

Item 201, furthermore, is a transparent substrate, 202 is a thin filmmetal layer, 203 is a mask, 204 is a photosensitive resin composition 1,205 is a photosensitive resin composition 2, 206 is ink, 207 is anovercoat resin, 209 is a color filter, 210 is a common electrode, 211 isan orientation film, 212 is an liquid crystal composition, 213 is apixel electrode, 214 is a glass substrate, 215 is a polarization panel,216 is light from a back light, 217 is a pixel ink cross-sectionimmediately after deployment, 218 is a pixel ink cross-section afterprebaking, 219 is a final ink cross-section when the drying conditionsare appropriate, 220 is a final ink cross-section that has become convexwhen the drying conditions are not appropriate; and 221 is a final inkcross-section that has become convex when the drying conditions are notappropriate.

Item 310, furthermore, is a substrate, 320 is a light blocking region,322 is a light blocking layer, 324 is a bank layer, 330 is alight-transmitting region, 332 is a coloring layer, 332 a is alight-transmitting part, 332 b is a non-transmitting part, 340 is anovercoat layer, 350 is a common electrode, 352 is a pixel electrode, 360and 362 are orienting films, 370 is a liquid crystal layer, 380 is asubstrate, 390 and 392 are polarization panels, 300 is a color filter,1000 is a liquid crystal display device, 2000 is a digital still camera,and 3000 is a personal computer.

BEST MODE FOR CARRYING OUT THE INVENTION EMBODIMENT 1

A color filter manufacturing process is now described with reference toFIG. 1.

Thin Film Forming Step (FIG. 1(A))

This step is a step for forming a chromium film 120 and a resist 130 ona substrate 110. The material used for the substrate 110 can be a glasssubstrate, plastic film, or plastic sheet, etc. For the substrate 110, aflat transparent glass substrate is prepared, measuring approximately370 mm×470 mm×1.1 mm, for example. This transparent glass substrateshould be able to withstand heat to a temperature of 350° C., be highlyresistant to such chemicals as acids and alkalis, and be capable of massproduction. Argon gas is used in sputtering a chromium target to formthe chromium film 120 on the substrate 110. The film thickness is made0.15μ. This chromium film 120 is patterned in prescribed demarcationregions in a step described subsequently, and functions as a blackmatrix comprising openings in the pixel regions. Next, a positive typephotosensitive resist 130 is spin-coated onto the chromium film 120. Thefilm thickness of this resist 130 is made 2.5μ. In addition to chromium,either nickel, tungsten, tantalum, copper, or aluminum may be used forthe black matrix material.

Etching Step (FIG. 1(B))

This step is a step for etching the chromium film 120, using the resist130 as a mask, to form banks 112. After applying the photosensitiveresist 130, the entire surface is subjected to a one-shot exposure in aprescribed demarcation pattern and developed. Next, the chromium film120 is etched with an aqueous solution of ammonium cerium nitrate andperchlorate, using the resist 130 as a mask, to form openings 111. Thepattern in which these openings 111 are formed may be suitably selectedfrom among a mosaic arrangement, delta arrangement, or stripedarrangement, etc. The shapes of the openings are not limited torectangular, but may be circular to match the shape of the ink drops. Bythis step, the banks 112 are formed (to a film thickness of 2.65μ), madeup of the chromium film 120 and the resist 130. These banks 112 functionas partitioning members for the openings 111.

In the step described above, furthermore, the resist pattern obtained bydeveloping the resist 130 is separated from the chromium film 120 with achemical treatment or an ashing treatment using oxygen plasma or thelike, and the demarcation-formed chromium pattern is exposed to thesubstrate surface. A resist or polyimide may be applied to that chromiumpattern, and patterned in a photolithograpic process so that it issuperimposed on the chromium pattern to form the banks 112.

Surface Treatment Step (FIG. 1(C))

This step subjects the substrate surface to a plasma treatment, andthereby imparts ink affinity to the substrate 110 and ink repellency tothe banks 112. The upper part (resist 130) of the banks 112 isconfigured of an insulative organic material, and the substrate 110 isconfigured of an inorganic material such as glass, wherefore the effectdescribed above is obtained by subjecting the substrate surface to aplasma treatment using a gas containing a fluorine-based compound as theinduction gas. More specifically, with a capacitive coupling type plasmatreatment, the induction gas is made to flow to a reaction chamber, oneelectrode 101 is connected to the substrate 110, another electrode 102is made to oppose the surface of the substrate 110, and a voltage isapplied from a power supply 103.

First, a plasma treatment is performed for 10 to 300 seconds, usingoxygen (O₂) as the induction gas, under conditions of a gas flow volumeof 500 SCCM, power of 0.1 W/cm² to 1.0 W/cm², and pressure of 1 Torr orless. With this step an ashing treatment is performed for the openings111, with ink affinity realized by the substrate 110 exposed to thesurface being activated.

Next, a plasma treatment is performed for 600 to 3600 seconds, usingcarbon tetrafluoride (CF₄) as the induction gas, under conditions of agas flow volume of 900 SCCM, power of 0.1 W/cm² to 1.0 W/cm², andpressure of 1 Torr or less. By this step, the surface energy of thebanks 112 can be lowered, making it easy to repel ink. Accordingly, thebanks 112 can be made semi-permanently ink-repellent while keeping theink affinity of the surface of the substrate 110.

Moreover, when conducting the plasma treatment with the fluorine-basedcompound gas, nitrogen trifluoride (NF₃) or sulfur hexafluoride (SF₆) orthe like can be used instead of carbon tetrafluoride (CF₄). It is alsopossible to use a heat treatment to restore the banks 112, after oncebeing activated with the oxygen plasma, to their original inkrepellency.

The substrate surface can be modified by the surface treatmentsdescribed in the foregoing, but it is particularly desirable that thecontact angle between the inks and the banks 112 be set from 30 degreesto 60 degrees, and that the contact angle between the inks and thesubstrate 110 be set to 30 degrees or less.

The preferred range for the contact angle between the inks and the banks112 can be derived as a result of the tests described below. In thesetests, the film thickness conditions of ink films are measured with thecontact angle between the ink and the glass substrate at 15 degrees, andthe contact angle between the banks and the inks set at 15 degrees, 33degrees, and 64 degrees (respectively). The results of these tests arediagrammed in FIG. 3. In this figure, the symbol 105 represents the filmthickness of the bank BM and the ink film IL, while the symbol 106indicates a bottom line indicating the ideal film thickness for the inkfilm IL.

At (A) in FIG. 3 is represented the case where the contact angle betweenthe ink and the banks BM is 15 degrees. Here it can be confirmed thatthe film thickness is inadequate in the center part of the ink film IL.For that reason, color loss occurs in the center part of the ink filmIL. The reason for this is thought to be that the quantity of inkadhering to the banks BM is great because the affinity between the inkand the banks BM is high, whereupon ink does not spread adequatelyinside the opening. It is undesirable that the coloring by the ink be inthis condition because that will become a cause of reducing the contrastin the liquid crystal display device.

At (B) in FIG. 3 is represented the case where the contact angle betweenthe ink and the banks BM is 33 degrees. Here it can be confirmed thatthe ink spreads throughout the opening, and that color loss does notoccur. This is thought to be because coloring irregularities do notarise because of the good balance between the ink repellency between theink and the banks BM, on the one hand, and the ink affinity between theink and the substrate, on the other.

At (C) in FIG. 3 is represented the case where the contact angle betweenthe inks and the banks BM is 64 degrees. Here it can be confirmed thatcolor loss occurs in the ink film IL in the vicinity of the banks BM.This is thought to happen because color loss occurs in the ink film ILin the vicinity of the banks BM due to the high ink repellency of thebanks BM. In view of these results, it is believed that the contactangle between the inks and the banks should be set at from 30 degrees to60 degrees.

The preferred range for the contact angle between the inks and thesubstrate 110 can be derived as a result of the following reasoning.FIG. 4 is a diagram for finding the surface area S of an ink drop formedunder the conditions of a contact angle θ between the substrate and theink and a contact width d between the substrate and the ink. From thisdiagram, the surface area S can be derived by drawing the area of theright triangle from the area of the fan shape. This surface area S maybe calculated as follows.

$S = {\frac{d^{2}}{4}\left( {\frac{\theta}{\sin^{2}\theta} - \frac{1}{\tan\;\theta}} \right)}$In FIG. 5 is diagrammed the relationship between the contact angle θ(degrees) of the ink to the substrate and the surface area S (μ³/μ) ofan ink drop when the value of d in the formula above is varied within arange of 5μ to 100μ. In FIG. 5, the symbol A represents the case whered=100μ, B the case where d=90μ, C the case where d=80μ, D the case whered=70μ, E the case where d=60μ, F the case where d=50μ, G the case whered=45μ, H the case where d=40μ, I the case where d=35μ, J the case whered=30μ, K the case where d=25μ, L the case where d=20μ, M the case whered=15μ, N the case where d=10μ, and O the case where d=5μ.

When the ink drops discharged from the ink jet printing head (EpsonMJ-500C) measure 571μ³ per drop and the pixel region pitch in the colorfilter is 80μ, the contact angle with the substrate will be seen to be28 degrees from FIG. 5. Because ink affinity is desired between thesubstrate and the inks, the contact angle between the inks and thesubstrate should be set at 30 degrees or less.

Furthermore, in order to establish the contact angle between the inksand the banks within the range noted above, it is well to add afluorine-based surfactant to the resist 130 such, for example, as onewith a structure having a fluorine-containing group such asperfluoroalkyl and its derivatives, fluorobenzene, difluorobenzene,trifluorobenzene, perfluorobenzene, or fluorophenol and its derivatives.By adding that fluorine-based surfactant to the resist 130, the surfaceenergy of the resist 130 can be lowered so that ink is more readilyrepelled. The inventors were able to verify as a result of testing thatresists 130 to which these surfactants were added functioned adequatelyas resist films (in terms of resistance to etching and bondability withthe chromium film 120). By suitably adjusting the amounts of thesesurfactants added, the contact angle between the banks and the inks canbe set within a range of 20 degrees to 60 degrees.

For the resist 130, moreover, a resist that is blended with afluorine-based polymer such, for example, as a silicone rubber, vinylpolyfluoride, fluoroolefin, vinyl-ether-based copolymer, ethylenetrifluoride, vinylidene fluoride copolymer, polytetrafluoroethylene,perfluoroethylene propylene resin, or perfluoroalcoxy resin. By blendingthe fluorine-based polymer into the resist 130, the surface energy ofthe resist 130 can be lowered so that ink is more readily repelled. Theinventors were able to verify as a result of testing that resists 130 towhich these polymers were blended functioned adequately as resist films(in terms of resistance to etching and bondability with the chromiumfilm 120). By suitably adjusting the ratios in which these polymers areadded, the contact angle between the banks and the ink can be set withina range of 2 degrees to 57 degrees. These contact angles are the valueswhen the coefficient of viscosity of the ink is η=4.30 cPs and thesurface tension thereof is γ=29.3 mN/m.

Ink Filling Step (FIG. 1.(D))

This step is a step for blowing ink into the openings 111 by the ink jetmethod and coloring the pixels R, G, and B. A pressurizing chamber inthe ink jet printing head 104 is filled with ink, the pressure in thepressurizing chamber is increased by the drive of an actuator such as apiezoelectric thin film device or the like, and ink drops 140 aredischarged. Because the upper part of the banks 112 is treated for inkrepellency, the ink can be prevented from crossing over the banks 112and flowing into the neighboring openings 111 and from running. Theheight of the banks 112 may be determined in view of the ink volumerequired for coloring, and can easily be adjusted by the thickness ofthe resist 130.

After the ink drops are loaded in the openings 111, a heat treatment isadministered with a heater. This heating is done at a temperature of110° C., for example, to vaporize the solvent in the ink. When thisprocess is done, only the solid components in the ink remain, and a filmis formed. Thus a component can be added to the ink so that it is eitherhardened by heating, considering the steps subsequent to coloring, or,alternatively, so that it is hardened by the energy of ultravioletradiation or the like. The component used for hardening by heating maybe any of various thermally hardening resins. The component used forhardening by energy may be an acrylate derivative or methacrylatederivative to which a photoreaction starting agent has been added, orthe like. Taking heat resistance into consideration, a component havingmultiple acryloyl groups or methacryloyl groups in the molecule ispreferable.

Protective Film Forming Step (FIG. 1(D))

This step is a step for forming a protective film so that it will coverthe ink films. After forming the ink films, heating is performed for aprescribed time (30 minutes, for example) at a prescribed temperature(200° C., for example) in order to completely dry the ink drops. Whenthis drying is complete, the protective film 150 is formed on the colorfilter substrate on which the ink films have been formed. Thisprotective film 150 also serves to smooth the surface of the filter. Amethod such as spin coating, roller coating, or dip coating, etc., isused in forming the protective film 150. In terms of the composition ofthe protective film 150, use may be made of a photo-hardening resin,thermally hardening resin, combination photo-thermally hardening resin,or an inorganic material or the like formed by vapor deposition orsputtering, etc. Taking transparency when used as a color filter intoaccount, these materials can be used so long as they can withstand thesubsequent ITO formation process and orientation film formation process,etc. If the protective film 150 is applied by spin coating, it is thenheated for a prescribed time (60 minutes, for example) at a prescribedtemperature (220° C., for example, to dry it.

Furthermore, by making the composition of the protective film 150 andthe composition of the resist 130 the same, the formation of crawlingand irregularities in the protective film 150 formed on the banks 112can be prevented. In that case, AHPA (bisphenol A) or FHPA (bisphenolfluorolene) and the like can be used as the material of the protectivefilm 150. In order to form the protective film 150 of these materials,first the substrate 110 is subjected to purification washing, and anamino silane treatment is done, after which the AHPA etc. is spin-coatedonto the substrate surface. Next, the processes of prebaking (10 minutesat 80° C.), leveling (10 minutes at 150° C.), and postbaking (60 minutesat 200° C.) are performed and the protective film 150 is formed.

Transparent Electrode Formation Step (FIG. 1(F))

Next, using a commonly known procedure such as sputtering or vapordeposition, the transparent electrode 160 is formed over the entiresurface of the protective film 150. As to the composition of thistransparent electrode 160, a material may be used such as ITO (indiumthin oxide) or a composite oxide of indium oxide and zinc oxide or thelike which combines both light transmissivity and electricalconductivity.

The color filter substrate can be fabricated by undergoing the stepsdescribed in the foregoing. A color liquid crystal panel is generallyfabricated by placing a color filter substrate and an opposing substratetogether in opposition, and sealing a liquid crystal compound betweenthe two substrates. On the inner side of the opposing substrate in theliquid crystal panel are formed thin film transistors and pixelelectrodes in a matrix pattern. In addition, an orienting film is formedinside the surfaces of the two substrates, and, by subjecting that to arubbing treatment, the liquid crystal molecules can be arranged in acertain direction. A polarizing panel is bonded to the outside of therespective glass substrates, and the liquid crystal compound is filledinto the gap between these glass substrates. For the back light, acombination of a fluorescent bulb and a scattering plate is commonlyused, and color displays are effected by causing the liquid crystalcompound to function as an optical shutter that varies thetransmissivity of the light from the back light.

It is also possible to apply this first embodiment to a manufacturingprocess for electroluminescence devices. More specifically, when usingan ink jet method for coloring thin film materials that configure a holetransport layer, light emission layer, and electron transport layer,etc., in pixel regions enclosed by banks, the substrate surface designprocesses (i.e. the processes of imparting ink repellency to the banksand ink affinity to the substrate) are made easier when the bankstructure is made the structure described in the foregoing.

As based on this first embodiment, the banks are given a two-layerstructure comprising a chromium film and a resist, wherefore thesubstrate surface design processes are made easy. Because the resistused in the process of etching the chromium film is not removed butrather left as is when forming the banks, the manufacturing processescan be simplified.

(Modification 1)

The manufacturing process for a color filter according to a firstmodification of the first embodiment is now described with reference toFIG. 2 (A1 to A3). What is different in this modification from the colorfilter described above is that the banks 112 are given a structurewherein a photosensitive polyimide film 170 and chromium film 120 arelaminated. First, the chromium film 120 is formed to a film thickness of0.15μ on the substrate 110 by sputtering, and the photosensitivepolyimide film 170 is formed thereon, over the entire surface (FIG.2(A1)). The photosensitive polyimide film 170 is then exposed accordingto the pixel region pattern, and developed to remove the unnecessaryportions (FIG. 2(A2)). The chromium film 120 is etched, using thephotosensitive polyimide film 170 as a mask, and the openings 111 areformed. In this step the banks 112 comprising the chromium film (lowerlayer) and photosensitive polyimide film (upper layer) are formed (FIG.2(A3)). After that, the color filter substrate is fabricated accordingto the steps diagrammed in (C) to (F) in FIG. 1.

Based on this first modification, because the banks are given thetwo-layer structure comprising the chromium film and the photosensitivepolyimide film, the substrate surface design processes (i.e. treating togive the banks ink repellency and give the substrate ink affinity) aremade easy. Also, because the banks are formed without removing thephotosensitive polyimide film that functions as the mask in the chromiumfilm etching step, leaving it remaining as is, the manufacturingprocesses can be simplified.

Besides the photosensitive polyimide film, moreover, a photosensitiveorganic material such as a polyimide film, acrylic resin film,polyhydroxy styrene film, novolac resin film, polyvinyl alcohol film, orcald resin film or the like can be used.

(Modification 2)

The manufacturing process for a color filter according to a secondmodification of the first embodiment is now described with reference toFIG. 2 (B1 to B4). What is different in this second modification fromthe color filter described above is that the banks 112 are given astructure wherein a photosensitive polyimide film 170, resist 130, andchromium film 120 are laminated. First, on the substrate 110 are formedthe chromium film 120 (to a film thickness of 0.15μ) and the resist 130(FIG. 2(B1)). The resist 130 is patterned, and, using that as a mask,the chromium film 120 is etched (FIG. 2(B2)). Then the photosensitivepolyimide film 170 is applied to the entire substrate surface withoutremoving the resist 130 (FIG. 2(B3)), and exposed and developed with thesame pattern as the chromium film 120, and the unnecessary portions areremoved (FIG. 2(B4)). After that, the color filter substrate isfabricated according to the steps diagrammed in (C) to (F) in FIG. 1.

Based on this second modification, the banks are formed of a pluralityof photosensitive organic materials, wherefore the substrate surfacedesign processes are made easy by combining these photosensitive organicthin films.

EMBODIMENT 2

A color filter manufacturing process according to a second embodiment ofthe present invention is now described with reference to FIG. 6. Theinitial step is diagrammed in FIG. 6( a). Here, for the material thatforms the light blocking thin film metal layer on the transparentsubstrate 201, a metal such as chromium, nickel, or aluminum is used,all of which are often used in electronic device fabrication processes.A thin film thereof is caused to adhere to the transparent substrate bya dry plating process to yield a light blocking layer 202. Adequatelight blocking performance is obtained if the thickness thereof is 0.1μor greater, but the limit is 0.5μ in view of concerns about thebondability and brittleness of the metal coating film obtained. Themetal may be any metal whatever, and may be selected from a wide range,giving consideration to the ease of thin film formation and theefficiency of the entire process including photoresist etching.

Next, as diagrammed at (b) and (c) in FIG. 6, the thin film metal layerin the pattern demarcation gap portions that will become the pixel unitson the transparent substrate are removed by a photoresist etchingprocess, and the required matrix pattern shape is obtained (FIG. 6( d)).

If the metal thin film light blocking layer described above is made thefirst layer, then a resin bank layer 205 for demarcating a second layermatrix pattern superimposed thereon is formed within a thickness rangeof 1.5 to 5μ (FIG. 6( e)). The role of the second layer is to partitionthe matrix pattern gaps where the inks are to be provided, acting asbanks, and to prevent mutual color mixing between adjacent inks. Aphotosensitive resin composition is used as the resin. Then, using aphotoresist process, the resin is removed from the matrix pattern gapportions where the inks are to be provided (FIGS. 6( f) and 6(g)).

The matrix pattern must be such that the first layer pattern and secondlayer pattern are superimposed. In terms of the precision of thissuperimposing, on average the first layer pattern width minus the secondlayer pattern width is plus 5μ, so the first layer pattern width isgreater than the second layer pattern width. The bank height in thefirst layer is determined in relationship to the film thickness of theink coating film formed in the pixels. The photosensitive resincomposition for the second layer may be selected from a wide range ofcompositions that have an especially large contact angle with water andexhibit outstanding water repellency, and is not limited to a blackcomposition. In the case of the present invention, the object can beattained using a urethane or acrylic photo-hardening type photosensitiveresin composition.

The surface is adjusted prior to deploying the ink by dry etching thesubstrate surface after the patterning described in the foregoing isfinished. It is possible to obtain the desired dry etching effect usingeither UV irradiation or atmospheric pressure plasma irradiation, butthe atmospheric pressure plasma etching method is more suitable forconfiguring the steps in a production line.

Next, as diagrammed in FIG. 6( h), inks are deployed in the matrixpattern gaps. For the method of deploying the inks, an ink jet method isemployed that involves a printing head used in an ink jet printing mode.As a method for forming ink coating films precisely in areas that are assmall as 50μ square, the ink jet printing method is ideal and effective,being able to make the discharged ink drops very minute and to controlthe number of ink drops discharged.

In order to deploy the very minute ink drops with good precision to thetargeted positions 206, that is, in the matrix pattern gaps, it is firstnecessary to control the size of the ink drops so that they match thesize of the targeted matrix pattern gaps. Good results were obtained bycontrolling the size of the ink drops to from 6 to 30 picoliters for a50μ² pixel size. Considering throughput, 12 to 20 picoliters ispreferable, wherewith good results were obtained. In order to cause theink drops to fly from the ink jet printing head and arrive at and adhereto the target accurately, conditions must be further managed so that theink drops fly straight and do not break up during flight.

In this second embodiment, after the deployed ink coating films haveadhered, dried, and hardened, means are provided for improving theleveling performance during the drying process so that thicknessuniformity is realized, as diagrammed in FIG. 6( i).

One of the means is a method wherein a solvent having a high boilingpoint is added to the deployed ink to reduce the drying speed. Suchsolvents having a high boiling point include butylcarbitol acetate,methoxybutyl actate, ethoxyethyl propionate, and methoxy-2-propylacetate. But this poses no limitation, and the solvent can be selectedfrom a wide range of solvents having a boiling point of from 150 to 300°C., taking pigment diffusability and dye solubility or the like intoconsideration.

Another of the means is a method that controls the drying speed of thedeployed ink. After the ink has been deployed, evaporation proceedsbeginning from the solvent components of low boiling point, theviscosity rises while leveling is being done, and the resin portioncontaining the pigment or dye is crosslinked and hardened by heat. Thedrying conditions are applied according to the ink properties bycombining setting in a natural atmosphere or prebaking at 40 to 100° C.,and final baking at 150 to 300° C. The shape designated 217 in FIG. 8(a), which is the pixel cross-sectional shape immediately after deployingthe ink, passes through the shape designated 218 during drying andbecomes the flat coating film 219. The inks possess their own particularviscosities, surface tensions, and fluid characteristics, respectively,and the range and combination of drying conditions noted above must beapplied according to the properties peculiar to the inks in order toobtain uniform film thickness after drying. If the drying and hardeningconditions do not match the ink properties, the deployed ink coatingfilm thicknesses will become uneven, as indicated by 220 in FIG. 8( b)or 221 in FIG. 8( c), which in turn will cause variation in pixel colortone.

After the pixel color material coating films have been formed, anovercoat 207 is formed to obtain a smooth surface, as diagrammed in FIG.6( j). Then a thin film common electrode 210 is formed on that surface,as diagrammed in FIG. 6( k), and the color filter is completed.

In FIG. 7 is diagrammed a cross-section of a TFT color liquid crystaldisplay device which incorporates the color filter described in theforegoing according to this second embodiment. The mode thereof is notlimited to this example, however.

A color liquid crystal display device is generally configured bycombining a color filter substrate 209 and an opposing substrate 214,and sealing in a liquid crystal composition 212. TFT (not diagrammed)and a thin film pixel electrode 213 are formed in a matrix pattern onthe inside of one of the substrates 214 of the liquid crystal displaydevice. As the other substrate, a color filter 209 wherein red, green,and blue pixel color materials are arranged is deployed in a position inopposition to the pixel electrode.

An orientation film 211 is formed inside the two substrate surfaces. Bysubjecting this orientation film 211 to a rubbing treatment, the liquidcrystal molecules can be lined up in one direction. A polarizing panel215 is bonded on the outside of each of the substrates, and the liquidcrystal composition 212 is filled into the gap between these substrates.The combination of a fluorescent bulb (not diagrammed) and a scatteringplate is commonly used for the back light, and displays are effected bycausing the liquid crystal compound to function as an optical shutterthat varies the transmissivity of the light from the back light.

This second embodiment 2 is now described in greater detail in terms ofembodiment examples.

EXAMPLE 1

The surface of a non-alkaline transparent glass substrate having athickness of 0.7 mm, and measuring 38 cm vertically and 30 cm across,was washed with a washing solution made by making a 1% addition of hotconcentrated sulfuric acid to hydrogen peroxide, rinsed with pure water,and subjected to air drying to obtain a clean surface. On this surfacewas formed a chromium coating film, by sputtering, to an average coatingfilm thickness of 0.2μ, to yield a light blocking coating film layer. Tothis surface was applied the photoresist OFPR-800 (made by Tokyo Ohka)by spin coating. To this substrate surface a matrix film havingdescribed thereon a prescribed matrix pattern was made to tightlyadhere, and this was subjected to UV exposure. Next, this was immersedin an alkaline developing fluid of 8% potassium hydroxide, and theunexposed photoresist in the pixel portions was removed. Followingthereupon, the exposed pixel-unit chromium coating film was removed byetching with an etching fluid having hydrochloric acid as the maincomponent. Thus a chromium thin film light blocking layer (black matrix,abbreviated BM) was obtained that is the first layer of the matrixpattern.

Onto this substrate, as the second layer, a positive type transparentacrylic photosensitive resin composition was applied, again by spincoating. After subjecting this to prebaking for 20 minutes at 100° C., aUV exposure was made using a revised version of the mask used inpatterning the chromium matrix pattern. The resin in the pixel portionsconstituting the unexposed portions was developed, again using analkaline developing fluid, and this was rinsed in pure water and thenspin-dried. Afterbaking was conducted for 30 minutes at 200° C. as thefinal drying step, and the resin portion was thoroughly hardened. Theaverage thickness of this resin layer coating film was 3.5μ.

In order to enhance the ink wettability of the gaps that would form thepixels, in the two-layer matrix pattern obtained, a dry etching process,that is, an atmospheric pressure plasma treatment was performed. A gasmixture made by adding 20% oxygen to helium was compressed to highpressure, a plasma atmosphere was formed at an atmospheric pressureetching spot, etching was performed by making the substrate to passbelow that spot, and both the bank resin parts and pixel units weresubjected to an activating treatment. Immediately after that treatment,the contact angle for water with a comparison test plate was an averageof 30° on the glass substrate over against an average 50° on the resincoating film.

To the pixel portions in the pattern gaps on this substrate, the inksconstituting the color materials were applied by being discharged underhigh-precision control from an ink jet printing head. A precision heademploying a piezoelectric effect was used in the ink jet printing head,and the ink drops were ejected, selectively in the various colors, inminute drops of 20 picoliters, 3 to 8 drops per pixel. In order toenhance flight speed of ink drops to the pixel blanks that are thetargets from the head, and to prevent flight turning and broken up dropsrunning astray (called satellites), the physical properties of the inkare of course important, but so are voltage wherewith the piezo elementsin the head are driven, and the waveform thereof. Hence waveforms forwhich conditions were set beforehand were programmed and the inks weredischarged and applied simultaneously in the three colors, namely red,green, and blue.

To obtain the inks used, after diffusing an inorganic pigment in apolyurethane resin oligomer, cyclohexanone and butyl acetate were addedas solvents having low boiling points and butylcarbitol acetate wasadded as a solvent having a high boiling point, and 0.01% of a non-ionicsurfactant was also added as a diffusing agent, and the viscosity wasadjusted to 6 to 8 centipoise.

After this application, drying was conducted by performing by settingthe ink coating film layer by allowing the substrate to stand for 3hours in a natural atmosphere, then heating for 40 minutes on a hotplate at 80° C., and finally heating for 30 minutes at 200° C., thussubjecting the ink coating film to hardening processes. According tothese conditions, the variation in ink coating film thickness in thepixels could be suppressed to 10% or lower, and, as a result, the colordifference in ink color tone could be held down to 3 or lower.

To the substrate described above, a transparent acrylic resin coatingmaterial was applied as an overcoat by spin coating and a smooth surfacewas obtained. On the upper surface thereof, furthermore, an ITOelectrode film was formed in a prescribed pattern to make the colorfilter. The color filter so obtained passed various endurance tests suchas a heat cycle endurance test, ultraviolet irradiation test, andincreased humidity test, etc., and it was thus verified that this wasfully usable as a liquid crystal display device element substrate.

EXAMPLE 2

The surface of a non-alkaline transparent glass substrate having athickness of 0.7 mm, and measuring 38 cm vertically and 30 cm across,was washed with a washing solution made by making a 1% addition of hotconcentrated sulfuric acid to hydrogen peroxide, rinsed with pure water,and subjected to air drying to obtain a clean surface. On this surfacewas formed an aluminum coating film, by sputtering, to an averagecoating film thickness of 0.5μ, to yield a light blocking coating filmlayer. To this surface was applied the photoresist OFPR-800 (made byTokyo Ohka) by spin coating. To this substrate surface a matrix filmhaving described thereon a prescribed matrix pattern was made to tightlyadhere, and this was subjected to UV exposure. Next, this was immersedin an alkaline developing fluid of 8% potassium hydroxide, and theunexposed aluminum coating film and photoresist in the pixel portionswere removed simultaneously. Aluminum is soluble in an alkali, whereforethe etching step using the acid could be omitted, resulting in processsimplification.

Onto this substrate, as the second layer, a positive type transparentacrylic photosensitive resin composition was applied, again by spincoating. After subjecting this to prebaking for 20 minutes at 100° C., aUV exposure was made using a revised version of the mask used inpatterning the aluminum matrix pattern. The resin in the pixel portionsconstituting the unexposed portions was developed, again using analkaline developing fluid, and this was rinsed in pure water and thenspin-dried. Afterbaking was conducted for 30 minutes at 200° C. as thefinal drying step, and the resin portion was thoroughly hardened. Theaverage thickness of the resin layer formed was 4μ.

In order to enhance the ink wettability of the gaps that would form thepixels, in the two-layer matrix pattern obtained, dry etching was done,and a UV irradiation treatment was performed at a wavelength of 270 nm.Immediately after this irradiation treatment, the contact angle forwater with a comparison test plate was an average of 35° on the glasssubstrate over against an average 55° on the resin coating film.

To the pixel portions in the pattern gaps on this substrate, the inksconstituting the color materials were applied by being discharged underhigh-precision control from an ink jet printing head. A precision heademploying a piezoelectric effect was used in the ink jet printing head,and the ink drops were ejected and applied, in minute drops of 12picoliters, 3 to 8 drops per pixel, sequentially for the red, green, andblue colors. In order to enhance speed of ink drops to the pixel blanksthat are the targets from the head, and to prevent flight turning, andbroken up drops running astray (called satellites), the physicalproperties of the ink are of course important, but so are voltagewherewith the piezo elements in the head are driven, and the waveformthereof. Hence waveforms for which conditions were set beforehand wereprogrammed and the ink drops were discharged and applied.

To obtain the inks used, after diffusing an inorganic pigment in apolyacrylic resin oligomer, cyclohexanone and butyl acetate were addedas solvents having low boiling points and butylcarbitol acetate wasadded as a solvent having a high boiling point, and 0.05% of a non-ionicsurfactant was also added as a diffusing agent, and the viscosity wasadjusted to 6 to 8 centipoise.

After the inks were discharged and applied, the drying conditions werematched with the physical properties of each color of ink, and, afterthe red, green, and blue inks were deployed, drying and hardening wereperformed, setting those drying conditions sequentially. The fluidcharacteristics of the red and blue inks are Newtonian, whereupon dryingand hardening for each were implemented by setting in a naturalatmosphere for 2 hours, heating on a hot plate for 20 minutes at 90° C.,and finally heating in an oven for 45 minutes at 180° C. The fluidcharacteristics of the green ink are non-Newtonian and stronglythixotropic, wherefore, in implementing the drying processes, thesetting time was made long at 5 hours., and final baking was done in anoven at 200° C. for 30 minutes. Based on these conditions, the variationin ink coating film thickness in the pixels could be suppressed to 5% orlower, and, as a result, the color difference in ink color tone could beheld down to 2 or lower.

To the substrate described above, a transparent acrylic resin coatingmaterial was applied as an overcoat by spin coating and a smooth surfacewas obtained. On the upper surface thereof, furthermore, an ITOelectrode film was formed in a prescribed pattern to make the colorfilter. The color filter so obtained passed various endurance tests suchas a heat cycle endurance test, ultraviolet irradiation test, andincreased humidity test, etc., and it was thus verified that this wasfully usable as a liquid crystal display device element substrate.

EXAMPLE 3

Using the same transparent glass substrate as in the first exampledescribed earlier, after performing the surface treatment in the sameway, to the surface thereof a thin film nickel layer was formed to athickness of 0.3μ by a nickel sputtering process to yield a metal lightblocking layer. To this surface was applied the photoresist OFPR-800(made by Tokyo Ohka) by spin coating. The substrate was dried on a hotplate for 5 minutes at 80° C. to yield a photoresit coating. To thissubstrate surface a matrix film having described thereon a prescribedmatrix pattern was made to tightly adhere, and this was subjected to UVexposure. Next, this was immersed in an alkaline developing fluid of 8%potassium hydroxide, and the unexposed photoresist in the pixel portionswas removed. Following thereupon, the exposed pixel-unit nickel coatingfilm was removed by etching with an etching fluid having hydrochloricacid as the main component. Thus a nickel thin film light blocking layer(black matrix, abbreviated BM) was obtained that is the first layer ofthe matrix pattern.

Onto this substrate, as the second layer, a negative type transparentacrylic photosensitive resin composition was applied, again by spincoating. After subjecting this to prebaking for 10 minutes at 140° C., aUV exposure was made using a positive-negative reversed revised versionof the mask used in patterning the nickel matrix pattern. The resin inthe pixel portions constituting the exposed portions was developed,again using an alkaline developing fluid, and this was rinsed in purewater and then air-dried. Afterbaking was conducted for 20 minutes at200° C. as the final drying step, and the resin portion was thoroughlyhardened. The average thickness of this resin layer coating film was 3μ.

In order to enhance the ink wettability of the gaps that would form thepixels, in the two-layer matrix pattern obtained, a laser beam ashingtreatment was administered as the dry etching. Immediately after thisirradiation treatment, the contact angle for water with a comparisontest plate was an average of 30° on the glass substrate over against anaverage 55° on the resin coating film.

To the pixel portions in the pattern gaps on this substrate, the inksconstituting the color materials were applied by being discharged underhigh-precision control from an ink jet printing head. A precision heademploying a piezoelectric effect was used in the ink jet printing head,and the ink drops were selectively ejected, in minute drops of 10picoliters, 6 to 12 drops per pixel. In order to enhance flight speed ofink drops to the pixel blanks that are the targets from the head, and toprevent flight turning, and broken up drops running astray (calledsatellites), the physical properties of the ink are of course important,but so are voltage wherewith the piezo elements in the head are driven,and the waveform thereof. Hence waveforms for which conditions were setbeforehand were programmed and the inks were discharged and appliedsimultaneously in the three colors, namely red, green, and blue.

To obtain the inks used, after diffusing an organic pigment in apolyacrylic resin oligomer, butyl alcohol added as a solvent having alow boiling point while glycerin and ethylene glycol were added assolvents having high boiling points, and 0.01% of a non-ionic surfactantwas also added as a diffusing agent, and the viscosity was adjusted to 4to 6 centipoise.

After this application, drying was conducted by performing by settingthe ink coating film layer by allowing the substrate to stand for 3hours in a natural atmosphere, then heating for 40 minutes on a hotplate at 80° C., and finally heating for 30 minutes at 200° C., thussubjecting the ink coating film to hardening processes. According tothese conditions, the variation in ink coating film thickness in thepixels could be suppressed to 10% or lower, and, as a result, the colordifference in ink color tone could be held down to 3 or lower.

To the substrate described above, a transparent acrylic resin coatingmaterial was applied as an overcoat by spin coating and a smooth surfacewas obtained. On the upper surface thereof, furthermore, an ITOelectrode film was formed in a prescribed pattern to make the colorfilter. The color filter so obtained passed various endurance tests suchas a heat cycle endurance test, ultraviolet irradiation test, andincreased humidity test, etc., and it was thus verified that this wasfully usable as a liquid crystal display device element substrate.

EMBODIMENT 3

FIG. 9 is a partial plan that diagrams in model form a color filterrelating to a third embodiment of the present invention. FIG. 10 is apartial cross-section that diagrams in model form a portion cut alongthe A—A line in FIG. 9.

The color filter 300 relating to this embodiment comprises a transparentsubstrate 310, light blocking regions 320 that do not substantiallytransmit light (visible light), and light transmitting regions 330 thatare capable of transmitting light. The light blocking regions 320 eachhave a light blocking layer 322 and a bank layer 324 formed on thatlight blocking layer 322. The light transmitting regions 330, which areregions that are demarcated by the light blocking regions 320, each havea coloring layer 332 formed on the substrate 310.

The light blocking regions 320 are described first.

The light blocking layers 322 that configure the light blocking regions320 have a prescribed matrix pattern formed on the substrate 310. Thelight blocking layer 322 need only exhibit sufficient light blockingqualities and function as a black matrix, and the materials of which itis made, etc., are not particularly limited, so that metals and resinsand the like are usable therefor. A metal is preferred as the materialfor the light blocking layer 322, in the interest of being able toobtain adequate and uniform light blocking performance with a small filmthickness. There is no particular limitation of the metal used for thelight blocking layer 322, however, and that metal may be selected with aview to the efficiency of the overall process that includes filmformation and photoetching. For such metal, preference may be given tometals such as chromium, nickel, and aluminum, etc., which are commonlyused in electronic device fabrication processes. When the light blockinglayer 322 is configured of a metal, adequate light blocking performanceis obtained if the film thickness thereof is 0.1μ or greater, but,taking the bondability and brittleness of the metal layer intoconsideration, it is preferable that that film thickness be 0.5μ orless.

The bank layer 324, is formed on the light blocking layer 322, and has aprescribed matrix pattern. This bank layer 324 demarcates regions wherethe coloring layers are to be formed, and prevents intermixing (colormixing) between colors of adjacent coloring layers. Accordingly, thefilm thickness (height h (cf. FIG. 10)) of the bank layer 324 isestablished by such relationships as the height of the ink layers, sothat the inks injected as color materials when forming the coloringlayers will not overflow. From this perspective, the bank layer 324should be formed in a film thickness range of 1 to 5μ, for example.

Now, this third embodiment is characterized by the fact that the banklayer 324, in the plan-view pattern thereof, is formed one size smallerthan the light blocking layer 322. More specifically, the bank layer 324is formed so that the light blocking layer 322 is exposed by aprescribed width d about the periphery thereof (cf. FIG. 10). It ispreferable, moreover, for reasons given subsequently, that the exposedsurface 322 a on the upper surface of the light blocking layer 322 becontinuous.

The bank layer 324 is configured by a resin layer that can be processedby photolithography. Such a photosensitive resin as this need notnecessarily exhibit either outstanding water repellency such that thecontact angle with water is large, or light blocking properties, andthus can be selected from a wide range of resins. For the resin whichconfigures the bank layer 324, use may be made of a photosensitive resincomposition comprising, for example, a urethane resin, acrylic resin,novolac resin, cald resin, polyimide resin, polyhydroxy styrene, orpolyvinyl alcohol, etc.

Each of the coloring layers 332 comprises a plurality of coloring layers332R, 332G, and 332B having the colors red, green, and blue that make upthree primary colors of light. These coloring layers are deployed in aprescribed pattern of arrangement, such as a striped arrangement, deltaarrangement, or mosaic arrangement, with one pixel being configured byconnected coloring layers of three colors.

The coloring layers 332, as diagrammed in FIG. 10, are formed not onlyon the exposed surfaces 310 a of the substrate 310, but also on theexposed surfaces 322 a of the light blocking layers 322. And theportions formed on the exposed surfaces 310 a of the substrate 310(those portions hereinafter called “light transmitting portions”) 332 aconfigure light transmitting regions 330, which function substantiallyas coloring layers. By way of contrast, the portions positioned on theexposed surfaces 322 a of the light blocking layers 322 (those portionshereinafter called “non-light transmitting portions”) 332 b, due to thelight blocking layers 322, do not substantially transmit light from thesubstrate 310 side or light to the substrate 310 side, and so do notfunction as coloring layers.

Thus, by having the non-light transmitting portions 332 b that do notfunction as light transmitting regions 330 formed at the peripheraledges of the coloring layers 332, the film thickness of the lighttransmitting portions 332 a of the coloring layers 332 that do functionas light transmitting regions 330 can be made uniform. As a result,color tone irregularities caused by disparities in the film thicknessbetween different portions of the coloring layers can be prevented. Thereason why that is so is now explained. At the peripheral edges of thecoloring layers 332, that is, the portions that contact the bank layer324, because of the ink wettability relative to the surface of the banklayer 324, among other things, the film thickness will become eithersmaller or larger than the other portions. For that reason, it istechnically quite difficult to give the coloring layers 332 uniform filmthickness across their entire surfaces. According to this thirdembodiment, however, by superimposing the peripheral edges of thecoloring layers 332, where it is particularly hard to achieve uniformfilm thickness, on portions of the light blocking layers 322, theperipheral edges wherein the film thickness is difficult to control canbe made the non-light transmitting portions 332 b. As a result, theportions of uneven film thickness that cause color tone irregularitiesand the like to occur can be eliminated from the light transmittingregions 330.

Accordingly, the width d of the exposed surfaces 322 a of the lightblocking layers 322 should be established in consideration of suchfactors as the ink wettability towards the bank layer 324, the effectivesurface area of the light transmitting regions 330, the relationshipbetween the ink volume and the film thickness, the limitations on makingthe width of the bank layer narrow, and the ink adherence precision,etc., as discussed in the foregoing, with 1 to 10μ being preferable, and3 to 5μ being more preferable.

It is also desirable that the exposed surfaces 322 a of the lightblocking layers 322 be formed continuously in a ring shape along theperipheral edges of the coloring layers 332, that is, along theperipheral edges of the light blocking layers 322, in view of thedesirability of having the coloring layers 332 formed in portions havinguneven film thickness, as described in the foregoing.

In this third embodiment, furthermore, the peripheral edges at thebottom surface of the bank layer 324 are positioned inside from theperipheral edges of the light blocking layers 322, that is, the sidesurfaces of the bank layer 324 are drawn back from the side surfaces ofthe light blocking layers 322, wherefore steps are formed on the lightblocking layers 322. As will be described subsequently, these stepsfunction to prevent ink form flowing into neighboring coloring layerformation regions when the coloring layers 332 are being formed. As aresult, the occurrence of color mixing in the coloring layers can besuppressed.

(Color Filter Manufacturing Method)

An example of color filter manufacture is described next whilereferencing FIG. 11 and FIG. 12. FIGS. 11 and 12 are cross-sections thatrepresent, in model form, partial layer structures corresponding to theB—B line in FIG. 9 in each step.

(1) Light Blocking Layer Formation

First, as diagrammed in FIG. 11(A), a metal layer 3220 is built up on atransparent substrate 310, to a film thickness of 0.1 to 0.5μ, by a dryplating process such as sputtering, vapor deposition, or chemical vapordeposition, for example. Various metals such as chromium, nickel, oraluminum may be used as the material for the metal layer 3220, asdescribed earlier. Next, a resist layer R1 having a prescribed patternis formed by photolithography on the surface of the metal layer 3220.After that, etching is performed, using that resist layer R1 as a mask,and the metal layer 3220 is patterned. Thus, as diagrammed in FIG.11(B), a light blocking layer 322 having a prescribed matrix pattern isformed on the substrate 310.

(2) Bank Layer Formation

Next, as diagrammed in FIG. 11(C), a resin layer 3240 is formed on thesubstrate 310 whereon the light blocking layer 322 is formed. This resinlayer may be formed by a negative or positive type resist. This resistlayer 3240 comprises, for example, a urethane- or acrylic-basedphoto-hardening photosensitive resin. An exposure is then made, using aphotomask M1, and developing is done, thereby patterning the resin layer3240. Thus, as diagrammed in FIG. 11(D), the bank layer 324 is formed,and the light blocking regions 320 are formed. The configuration of thisbank layer 324 has already been described, so no further descriptionthereof is given here. In this step, coloring layer formation regions3330, demarcated by the light blocking regions 320, are formed in aprescribed matrix pattern.

Next, as necessary, the substrate surface is subjected to surfacetreatment prior to the next step wherein the coloring layers are formed.Ultraviolet irradiation, plasma irradiation, or laser irradiation andthe like may be used as the method of such surface treatment. Byperforming such surface treatment, contaminating substances adhering tothe exposed surfaces 310 a of the substrate 310 can be removed, and thecontact angle of these surfaces 310 a with water can be made smaller andthe ink wettability thereof improved. In more specific terms, it ispreferable that the difference in contact angle with water between theexposed surfaces 310 a of the substrate 310 and the surface of the banklayer 324 should be 15° or greater. Thus, by controlling the contactangles with water of the exposed surfaces 310 a of the substrate 310 andof the surface of the bank layer 324, not only can ink be deployed onthe exposed surfaces 310 a of the coloring layer formation regions 3330under good bonding conditions, but, due to the property whereby the banklayer 324 repels ink, ink can be prevented from crossing the bank layer324 and overflowing. For the method of surface treatment, dry etchingbased on atmospheric pressure irradiation is preferable in view of thesuitability for incorporating the step into a production line.

(3) Coloring Layer Formation

First, as diagrammed in FIG. 12(A), ink is deployed in a coloring layerformation region 3330 demarcated by the light blocking layers 322 andthe bank layer 324, to form an ink layer 3320. In this third embodiment,the method used for deploying this ink is an ink jet method involving aprinting head used in an ink jet printing mode. For a method for formingan ink layer with good precision in a minute coloring layer formationregion 3330 that is 50μ square, for example, an ink jet printing methodcapable of making the ink drops discharged very minute and alsocontrolling the number of ink drops discharged is ideal.

In order to deliver the very fine ink drops precisely to the targetedposition (i.e. the exposed surface 310 a of the substrate 310), firstthe size of the ink drops is controlled to match the size of the exposedsurface 310 a of the coloring layer forming region 3330 that is thetarget. The size of these ink drops should be controlled to 6 to 30picoliters for a coloring layer forming region 3330 measuring 50μsquare, for example. It is even more preferable that the size of the inkdrops be from 12 to 20 picoliters in the interest of throughput. Theconditions should also be controlled so that, when the ink drops arecaused to fly from the ink jet printing head that the conditions becontrolled so that those ink drops fly straight, without breaking up inflight, so that they will arrive at the target accurately.

With this third embodiment also, as was noted when describing the secondembodiment earlier, it is preferable that means be comprised forenhancing leveling during the drying of the ink layers. One example ofsuch means is the method of adding a solvent with a high boiling pointto the ink to slow down the drying speed. Another example of such meansis the method of controlling the drying conditions of the deployed ink.The drying conditions can be applied according to the ink properties bycombining setting in a natural atmosphere and/or prebaking at 40 to 100°C. (i.e. at least one of those processes) together with final baking at150 to 300° C.

In this third embodiment, the coloring layers 332 are sequentiallyformed in each color, namely red, green, and blue. There is noparticular limitation on the order in which these coloring layers 332are formed. In the example diagrammed in FIG. 12(B), first the greencoloring layer 332G is formed, then either the red coloring layer 332Ror the blue coloring layer 332B is formed, as diagrammed in FIG. 12(C),then the coloring layer of the remaining color is formed last of all.

In this third embodiment, because the side walls of the bank layer 324are drawn back from the side walls of the light blocking layer 322, astep is formed on the light blocking layer 322. For this reason, asdiagrammed in FIG. 12(A), when an ink layer 3320 is formed in a coloringlayer forming region 3330, even if a portion of that ink layer 3320overflows the bank layer 324, that ink will collect on the step formedby the side walls of the bank layer 324 and the exposed surface 322 a ofthe light blocking layer 322, and so will be prevented from flowing intothe exposed surface 310 a of the substrate 310 in the neighboringcoloring layer forming regions 3330. As a result, the occurrence ofcoloring layer color mixing due to ink mixing can be prevented.

The coloring layers in the red, green, and blue colors can also beformed simultaneously by selecting a color head or a plurality of headsin an ink jet printing system.

(4) Formation of Overcoat Layer, etc.

Next, as diagrammed in FIG. 12(C), after forming the coloring layers332, as necessary, an overcoat layer 340 is formed in order to obtain asmooth surface. Then, as diagrammed in FIG. 12(D), as necessary, acommon electrode 350 is formed on the overcoat layer 340, and the colorfilter 300 is completed. This overcoat layer 340 and common electrode350 can be provided according to the configuration of theelectro-optical device in which the color filter is to be employed.

(Operational Benefits)

The main operational benefits of the color filter of the thirdembodiment are now described.

(a) The bank layer 324 is formed so that, in its plan-view pattern, thewidth thereof is smaller than that of the light blocking layers 322, andportions of the light blocking layers 322 are exposed. By having theseexposed surfaces 322 a, non-light transmitting portions 332 b that donot function as light transmitting regions 330 are formed at theperipheral edges of the coloring layers 332 where it is difficult toobtain uniform film thickness. As a result, defects such as color toneirregularities do not readily develop in the color filter of this thirdembodiment, and high contrast is effected, because the film thickness ofthe light transmitting portions 332 a of the coloring layers 332 that dofunction as light transmitting regions 330 can be made uniform.

(b) By providing the light blocking layers 322 and the bank layer 324,the light blocking function and the demarcation function can each beestablished independently, wherefore both functions can be manifestedwithout fail. As a result, in the color filter of this embodiment, pixeldefects caused by inadequate light blocking or color mixing do notreadily develop. By dividing the functions in this manner, moreover,optimal materials for configuring the light blocking layers and banklayer can be selected from a wide range, which is beneficial also interms of production cost. When the light blocking layers 322 areconfigured of metal layers, in particular, light blocking performance isobtained that is both adequate and uniform with a small film thickness.

(c) In this third embodiment, the side walls of the bank layer 324 aredrawn back from the side walls of the light blocking layers 322,wherefore a step is formed on the light blocking layers 322. Ink can beretained by this step, furthermore, so that, even of a portion of an inklayer overflows the bank layer 324, that ink will be prevented fromflowing into the exposed surface 310 a of the substrate 310 inneighboring coloring layer formation regions. For that reason, theoccurrence of coloring layer color mixing due to ink mixing can beprevented. As a result, defects such as color tone irregularities do notreadily develop in the color filter of this embodiment, and highcontrast is effected.

As based on the manufacturing method for the color filter of thisembodiment, moreover, the following operational benefits are realized.

(a) Based on the manufacturing method for the color filter of thisembodiment, the color filter of this embodiment can be formed with fewsteps. More specifically, by forming the coloring layers with an ink jetmethod, the step of patterning using photolithography can be eliminated,and the process simplified. Also, because inks are made to adhere to thecoloring layers with the ink jet method, the inks can be delivered onlyto the necessary coloring layer forming regions. For that reason, thereis no loss of color materials as with patterning using photolithography,wherewith unnecessary portions are removed, and the cost of the colorfilters can be reduced.

(b) In this embodiment, by subjecting the substrate surface to surfacetreatment prior to forming the coloring layers, contaminating matteradhering to the exposed surface 310 a of the substrate 310 can beremoved, the contact angle of that surface 310 a with water can be madesmall, and ink wettability can be enhanced. Thus, by controlling thecontact angles with water of the exposed surface 310 a of the substrate310 and of the surface of the bank layer 324, ink can be deployed on theexposed surface 310 a of the coloring layer formation regions 3330 in acondition of good bonding, and, in addition, due to the ink repellingproperty of the bank layer 324, the ink is kept from crossing andoverflowing the bank layer 324. During the ink drying process, moreover,film thickness irregularities caused by ink being pulled to the banklayer are suppressed.

(Color Filter Modification)

FIG. 13 is a partial cross-section that represents, in model form, amodification of the color filter relating to this third embodiment. Thecolor filter 400 diagrammed in FIG. 13 corresponds to FIG. 10 thatdiagrams the color filter 300 described in the foregoing. In the colorfilter 400, for parts having substantially the same function as thecolor filter 300 diagrammed in FIGS. 9 and 10, the same symbols as wereused in FIGS. 9 and 10 are used, and no further description thereof isgiven here.

In the color filter 400 in this modification, the shape of the banklayer 324 is different than in the color filter 300 described earlier.In this modification, the cross-sectional shape of the bank layer 324 inthe width dimension forms a tapered configuration, having a roughlytrapezoidal shape with the width smaller at the upper end than at thelower end.

Because the bank layer 324 has such a tapered shape as this, thefollowing advantages are realized in addition to the operationalbenefits of the color filter 300 described earlier.

That is, by the bank layer 324 having such a tapered shape as this,adequate width can be secured in the upper part of the non-lighttransmitting portions 332 b of the coloring layers 332. As a result, thewidth of the exposed surfaces 322 a of the light blocking layers 322 canbe made relatively smaller, the effective surface area of the lighttransmitting regions 330 relative to the surface of the substrate 310can be made larger, and larger surface area capable of contributing tothe pixel regions can be secured.

The tapered bank layer 324 can be formed by the following method, forexample.

A photosensitive resin is coated uniformly over the entire surfacewhereon the light blocking layers are formed. Spin coating is a typicalmethod for this coating process, but a printing, film transfer, or barcoating method or the like may be used instead. A negative typephotomask is prepared, alignment exposure is performed, and the portionsirradiated by light are hardened by a reaction. Then if developing andbaking are performed, the bank layer is complete. The angle of banklayer taper can be controlled by adjusting the sensitivity of thematerial.

EMBODIMENT EXAMPLES

This third embodiment is now described in greater detail in terms ofexamples.

The surface of a transparent substrate made of non-alkaline glass andmeasuring 0.7 mm in film thickness, 38 cm vertically, and 30communication across was washed in a cleaning fluid of hot concentratedsulfuric acid to which 1 wt. % of hydrogen peroxide had been added,rinsed with pure water, and then air dried to yield a clean surface. Onthis surface was formed a chromium film having an average film thicknessof 0.2μ to obtain a metal layer. To the surface of this metal layer wasapplied the photoresist OFPR-800 (made by Tokyo Ohka) by spin coating.The substrate was dried for 5 minutes at 80° C. on a hot plate, and aphotoresist layer was formed. To the surface of this substrate, a maskfilm whereon the prescribed matrix pattern shape was drawn was made totightly adhere, and an exposure was made with ultraviolet light. Next,this was immersed in an alkaline developing fluid containing 8 wt. % ofpotassium hydroxide, the unexposed portions of the photoresist wereremoved, and the resist layer was patterned. Following thereupon, theexposed metal layer was removed by etching with an etching fluidcontaining hydrochloric acid as its main component. Thus was obtained alight blocking layer (black matrix) having a prescribed matrix pattern.The film thickness of the light blocking layer was about 0.2μ. The widthof the light blocking layer was about 22μ.

On this substrate a negative type transparent acrylic photosensitiveresin composition was also applied, again by spin coating. Afterprebaking for 20 minutes at 100° C., ultraviolet exposure was performedusing a mask film having a prescribed matrix pattern shape drawnthereon. The unexposed portions of the resin were developed with analkaline developing fluid, and the substrate was rinsed in pure waterand then spin dried. Afterbaking was conducted for 30 minutes at 200° C.as the final drying process, the resin portions were thoroughlyhardened, and the bank layer was formed. The average film thickness ofthis bank layer was 3.5μ. The width of the bank layer was about 14μ. Anda ring shaped exposure surface having a width of about 4μ was formed onthe upper surface of the light blocking layer.

In order to improve the ink wettability of the coloring layer formingregions demarcated on the bank layer and the light blocking layer, dryetching, that is, an atmospheric pressure plasma treatment wasperformed. A gas mixture in which 20% oxygen was added to helium wascompressed to a high pressure, a plasma atmosphere was formed into anetching spot within atmospheric pressure, the substrate was passed belowthat etching spot and etched, and both the bank layer and the coloringlayer formation regions (exposed surfaces of glass substrate) weresubjected to an activation treatment. Immediately after this treatment,the contact angle for water with a comparison test plate was an averageof 35° on the glass substrate over against an average 50° on the banklayer.

To these coloring layer formation regions, inks were applied,discharging the inks constituting color materials from an ink jetprinting head under high-precision control. A precision head employing apiezoelectric effect was used in the ink jet printing head, and the inkdrops were selectively ejected, in minute drops of 20 picoliters, 3 to 8drops per coloring formation region. In order to enhance flight speed ofink drops to the coloring layer formation regions that are the targetsfrom the head, and to prevent flight turning, and broken up dropsrunning astray (called satellites), the physical properties of the inkare of course important, but so are voltage wherewith the piezo elementsin the head are driven, and the waveform thereof. Hence waveforms forwhich conditions were set beforehand were programmed and the inks weredischarged and applied simultaneously in the three colors, namely red,green, and blue.

To obtain the inks used, after diffusing inorganic pigments in apolyurethane resin oligomer, cyclohexanone and butyl acetate were addedas solvents having low boiling points while butylcarbitol acetate wasadded as a solvent having a high boiling point, and 0.01 wt. % of anon-ionic surfactant was also added as a diffusing agent, and theviscosity was adjusted to 6 to 8 centipoise.

After this application, the ink layer was set by allowing the substrateto stand for 3 hours in a natural atmosphere, then heating was performedfor 40 minutes on a hot plate at 80° C., and finally heating wasperformed for 30 minutes at 200° C., thus subjecting the ink layer tohardening processes, and yielding the coloring layer. According to theseconditions, the variation in the film thickness in the coloring layer,and particularly in the light transmitting portions thereof, could besuppressed to 10% or lower, and, as a result, the color difference inink color tone in the coloring layer could be held down to 3 or lower,or even to 2 or lower.

To the substrate described above, a transparent acrylic resin coatingmaterial was applied by spin coating to obtain an overcoat layer havinga smooth surface. On the upper surface thereof, furthermore, anelectrode layer made of ITO was formed in a prescribed pattern, and acolor filter was made. The color filter so obtained passed variousendurance tests such as a heat cycle endurance test, ultravioletirradiation test, and increased humidity test, etc., and it was thusverified that this was fully usable as a an element substrate such as aliquid crystal display device.

(Electro-Optical Device)

In FIG. 14 is represented a cross-section of a color liquid crystaldisplay device, given as one example of an electro-optical deviceincorporating the color filter relating to the present invention.

A color liquid crystal display device 1000 is commonly configured byincorporating a color filter 300 and an opposing substrate 380, andsealing a liquid crystal composition 370 between the two. On the surfaceon the inner side of one substrate 380 of the liquid crystal displaydevice 1000, TFT (thin film transistor) elements (not shown) and pixelelectrodes 352 are formed in a matrix pattern. As the other substrate, acolor filter 300 is deployed, so that red, green, and blue coloringlayers 332 are arranged at positions in opposition to the pixelelectrodes 352. On the respective surfaces that are in opposition to thesubstrate 380 and the color filter 300, orientation films 360 and 362are formed. These orientation films 360 and 362 are subjected to arubbing treatment, and the liquid crystal molecules can be lined up inthe same direction. To the outside surfaces of the substrate 310 and thecolor filter 300, moreover, polarizing panels 390 and 392 are bonded,respectively. A combination of a fluorescent bulb (not shown) and adiffusion plate are usually used as the back light, and color displaysare effected by causing the liquid crystal compound to function as anoptical shutter that varies the transmissivity of the light from theback light.

(Electronic Equipment)

An example of electronic equipment wherein the color filters in thefirst, second, and third embodiments of the present invention are usedis now described.

FIG. 15 is a diagonal view showing the configuration of a digital stillcamera wherein a liquid crystal display device 1000 wherein the colorfilter relating to the present invention is employed is used as the viewfinder. This figure also shows in simple form how connections are madeto external equipment.

Whereas an ordinary camera exposes a film by the optical image of theobject being photographed, the digital still camera 2000 takes theoptical image of the object being photographed, makes a photoelectricconversion using an image pickup element such as a CCD (charge coupleddevice), and generates image pickup signals. Here, the liquid crystalpanel of the liquid crystal display device 1000 described above isdeployed on the back side (shown as the front side in FIG. 15) of thecase 2202 of the digital still camera 2000, in a configuration wherein adisplay is made based on image pickup signals from the CCD. For thisreason, the liquid crystal display device 1000 functions as a viewfinder which displays the object being photographed. On the front side(the back side as shown in FIG. 15) of the case 2202, a light receivingunit 2204 comprising an optical lens and CCD, etc., is deployed.

Here, the photographer verifies the object being photographed displayedon the liquid crystal display device 1000, and then depresses a shutterbutton 2206. Thereupon, the CCD image pickup signals at that point intime are sent to and stored in a circuit board 2208 memory. In thisdigital still camera 2000, furthermore, on the side surface of the case2202, video signal output terminals 2212 and a data communications I/Oterminal 2214 are provided. As necessary, moreover, as diagrammed inFIG. 15, a television monitor 2300 may be connected to the former, thatis, to the video signal output terminals 2212, and a personal computer2400 may be connected to the latter, that is, to the data communicationsI/O terminal 2214. Also, the image pickup signals stored in the circuitboard 2208 memory can be output to the television monitor 2300 or to thepersonal computer 2400, by making prescribed control inputs.

FIG. 16 represents a notebook type personal computer 3000 given asanother example of electronic equipment using the liquid crystal displaydevice 1000 wherein the color filter relation to the present inventionis employed is used as a display unit. As diagrammed in this figure, theliquid crystal display panel 1100 of the liquid crystal display device1000 is housed in a case 3100, in a configuration wherein the displayregion of the liquid crystal display pattern 1100 is exposed through anopening 3100A formed in the case 3100. The personal computer 3000 alsocomprises a keyboard 3300 as the input unit.

These pieces of equipment, namely the digital still camera 2000 and thepersonal computer 3000, have a liquid crystal display device 1000comprising the color filter relating to the present invention, whereforeimage displays can be made that exhibit high contrast, without colortone irregularities or other pixel flaws, and lower costs can also beeffected.

These pieces of electronic equipment are configured comprising, inaddition to the liquid crystal display device 1000, display signalgenerators comprising in turn various kinds of circuits such as displayinformation output sources, display information processing circuits, andclock signal generating circuits, and power supply circuits forsupplying electric power to those circuits. In the display unit, in thecase of the personal computer 3000, for example, display images areformed by the supply of display signals generated by a display signalgenerator on the basis of information and the like input from the inputunit 3300.

The electronic equipment wherein the liquid crystal display devicerelating to the present invention may be incorporated is not limited todigital still cameras and personal computers, but may be all kinds ofelectronic equipment such as electronic notebooks, pagers, POSterminals, IC cards, minidisc players, liquid crystal projectors,multimedia compatible personal computers (PCs) and engineeringworkstations (EWSs), word processors, television receivers, video taperecorders (whether of the viewfinder or direct monitor viewing type),electronic desktop calculators, automobile navigation equipment, devicescomprising a touch panel, clocks and watches, and game equipment.

Various types of liquid crystal panel may be used for the liquid crystaldisplay panel. In terms of the drive scheme, these include simple matrixliquid crystal display panels and static drive liquid crystal displaypanels that do not employ switching elements in the panel itself, andalso active matrix liquid crystal display panels that use eitherthree-terminal switching elements (typified by TFTs (thin filmtransistors)) or two-terminal switching elements (typified by TFDS (thinfilm diodes)). In terms of electro-optical characteristics, theseinclude the TN type, STN type, guest-host type, mutual transfer type,and ferroelectric type, etc.

Devices relating to the present invention have been described in termsof a number of specific embodiments therefor, but the present inventionis capable of various modifications within the range of its essentialfeatures. In the embodiments described in the foregoing, for example,the descriptions are for cases where an liquid crystal display is usedas the image display means (electro-optical display unit) in anelectro-optical apparatus. However, the present invention is not limitedthereto or thereby, but may instead use a thin type cathode ray tube, ora small television using an liquid crystal shutter or the like, or anelectro-luminescence display device, plasma display, CRT display, FED(field emission display) panel, etc.

The industrial usefulness of the present invention is now discussed.Based on the color filter of the present invention, the banks are givena laminar structure comprising a metal film and a photosensitive organicthin film, wherefore treating the substrate to impart ink affinity andtreating the banks to impart ink repellency are made easy. Inparticular, the ink repellency of the banks can be adjusted by adding afluorine-based surfactant to the photosensitive organic thin film ormixing in a fluorine-based polymer. Accordingly, a liquid crystaldisplay device comprising the color filters of the present inventionexhibit very fine characteristics without coloring or displayirregularities.

Based on the color filter manufacturing method of the present invention,color filters can be provided which comprise banks well suited to theink jet process. In particular, because the banks are used as they are,without removing the resist used to etch the metal film, themanufacturing process can be simplified, and low-cost color filters canbe manufactured.

Based on the present invention, inks can be deployed precisely and veryefficiently in very fine matrix pattern gaps by a precision-controlprinting head. By controlling the physical properties of the inks, andselecting drying conditions that match those physical properties afterthe inks have been deployed, uniformity of ink coating film thickness isobtained, and color tone irregularities can in practice be made a colordifference of 3 or lower. By applying an overcoat to this substrate, andforming a thin film electrode, the color filter is completed. By usingthis color filter, it is easy to obtain liquid crystal display devicesexhibiting outstanding color characteristics such as contrast usingenergy saving processes.

1. A method of manufacturing a color filter comprising: a step ofdemarcating and forming a metal film on a substrate; a step of formingbanks on the substrate by forming a plurality of photosensitive organicthin film layers on the metal film; a step of applying inks to each areaenclosed by said banks; a step of forming ink layers by drying said inksat a temperature of 200° C.; a step of forming a protective film thatcovers said banks and said ink layers; and a step of drying saidprotective film at a temperature of 220° C.
 2. The method ofmanufacturing a color filter according to claim 1, wherein a blackmatrix is formed in said banks.
 3. The method of manufacturing a colorfilter according to claim 1, wherein a composition of said banks is thesame as a composition of said protective film.
 4. A method formanufacturing a display device having a color filter, wherein said colorfilter is formed by a technique comprising: a step of demarcating andforming a metal film on a substrate; a step of forming banks on thesubstrate by forming a plurality of photosensitive organic thin filmlayers on the metal film; a step of applying inks to each area enclosedin said banks; a step of forming ink layers by drying said inks at atemperature of 200° C.; a step of forming a protective film that coverssaid banks and said ink layers; and a step of drying said protectivefilm at a temperature of 220° C.
 5. The method of manufacturing adisplay device according to claim 4, wherein a black matrix is formed insaid banks.
 6. The method of manufacturing a display device according toclaim 4, wherein a composition of said banks is the same as acomposition of said protective films.
 7. A method for manufacturing anelectronic device having a display device that has a color filter,wherein said color filter is formed by a technique comprising: a step ofdemarcating and forming a metal film on a substrate; a step of formingbanks on the substrate by forming a photosensitive organic thin filmlayer on the metal film; a step of applying inks to each area enclosedin said banks; a step of forming ink layers by drying said inks at atemperature of 200° C.; a step of forming a protective film that coverssaid banks and said ink layers; and a step of drying said protectivefilm at a temperature of 220° C.
 8. A method of manufacturing a colorfilter comprising: a step of demarcating and forming a metal film on asubstrate; a step of forming banks on the substrate by forming aphotosensitive organic thin film layer on the metal film; a step ofapplying inks comprising a solvent having a high boiling point to eacharea enclosed in said banks; and a step of forming ink layers by dryingsaid inks, wherein said step of forming ink layers comprises a processof setting or prebaking at a temperature of from 40 to 100° C., and aprocess of final baking at a temperature of from 160 to 200° C.